The patient, at Community Hospital in Muncie, Indiana, is a health care worker who had traveled from Saudi Arabia, where the virus was first seen.
"All of the tests in close contacts have been negative," Don Fesko, CEO of the hospital, told a news conference. Officials said about 50 health workers had contact with the patient before they began taking extreme measures -- wearing masks, gloves, gowns and eye protection.
"All of the tests in close contacts have been negative."
The patient is in good spirits, has been taken off supplementary oxygen, has been walking around and is cooperating with isolation precautions, officials said. Family members have been asked to isolate themselves and to wear face masks when they go out in public, just in case they are infected and haven't begun to show any symptoms yet.
The incubation period for MERS is usually about five days but it's been known to take as long as 14 days to cause symptoms, so the doctors are taking the most cautious approach.
Middle East Respiratory Sydrome (MERS) virus was first seen in 2012 and most cases are linked to the Middle East, although it's now been seen in more than a dozen countries around the world. Many of those who are sick enough to show symptoms have had other conditions, such as cancer, diabetes or kidney disease.
It spreads from person to person, but usually only with close and prolonged contact. But Centers for Disease Control and Prevention experts and state health officials are testing health care workers and other close contacts of the patients, and will continue to test them for 14 days, just to be sure.
"It appears MERS picked the wrong hospital, the wrong state, and the wrong country to take hold," said Indiana state health commissioner Dr. William VanNess.
Officials are tracking down about 100 passengers from an airplane the patient traveled on and 10 bus passengers to make sure they don't have any symptoms. But experts say MERS has not been known to pass from casual contact such as sitting next to someone on public transport.
Health officials are releasing very little information about the patient but say he lives and works in Saudi Arabia. "He was working at a hospital in Saudi Arabia," said Dr. Daniel Feikin, CDC's medical epidemiologist at the hospital.
"He does not recall directly working with a patient who had MERS although he did work in a hospital that had cases of MERS."
He came to the U.S. on April 24 and went to the emergency department at the hospital on the 28th.'